import sqlite3, json

class DB(sqlite3.Connection):
    def __init__(self, db_name="db.sqlite"):
        super().__init__(db_name)
        with self:
            self.execute('''
                CREATE TABLE IF NOT EXISTS kv_store
                (key TEXT PRIMARY KEY, value BLOB)
            ''')

    def __setitem__(self, key, value):
        if not isinstance(value, bytes): value = json.dumps(value)
        with self:
            cur = self.execute('''
                INSERT OR REPLACE INTO kv_store
                (key, value) VALUES (?, ?)
            ''', (key, value))
            return {"modified_count": cur.rowcount}

    def __getitem__(self, key):
        with self:
            result = self.execute('''
                SELECT value FROM kv_store
                WHERE key = ?
            ''', (key,)).fetchone()
        if result:
            if isinstance(result[0], str):
                try: return json.loads(result[0])
                except json.JSONDecodeError: pass
            return result[0]

    def delete(self, key):
        with self:
            cur = self.execute('''
                DELETE FROM kv_store 
                WHERE key = ?
            ''', (key,))
            return {"deleted_count": cur.rowcount}

    def keys(self, pattern='*'):
        pattern = pattern.translate(str.maketrans({
            '\\': '\\\\', '%': '\\%', '_': '\\_', '*': '%', '?': '_'
        }))
        with self:
            result = self.execute('''
                SELECT key FROM kv_store
                WHERE key LIKE ? ESCAPE '\\'
            ''', (pattern,)).fetchall()
        return [row[0] for row in result]

    def __repr__(self): return repr(self.keys())

    def exists(self, key):
        with self:
            cur = self.execute('''
                SELECT 1 FROM kv_store
                WHERE key = ?
                LIMIT 1
            ''', (key,))
            return bool(cur.fetchone())